The present invention relates to the field of network communications. More particularly, in one embodiment the present is invention provides a method and apparatus for dynamically shifting between switching and routing packets efficiently to provide high packet throughput while maintaining complete Internet Protocol (IP) routing functionality. The present invention combines high speed, capacity, multiservice traffic capability, with simplicity, scaleability, and robustness.
Due to the current popularity and continual growth of the Internet, which utilizes IP, IP has evolved into the dominant network-layer protocol in use today. IP specifies protocol data unit (PDU) format and station-router and router-router interaction. IP provides a connectionless data transfer service to IP users in stations attached to networks of the Internet. The connectionless model on which IP is based provides a robust and flexible basis on which to construct an integrated services network. All major operating systems include an implementation of IP, enabling IP and its companion transport-layer (Layer 4 of the OSI reference model) protocol, the Transmission Control Protocol (TCP), to be used universally across virtually all hardware platforms. One of the major advantages of IP is its tremendous scaleability, operating successfully in networks with only a few users to enterprise-size networks, including the global Internet.
With the rapid growth of the Internet, conventional IP routers are becoming inadequate in their ability to handle the traffic on the Internet. With today's faster workstations, client-server computing, and higher bandwidth requirement applications, networks are increasingly encountering traffic congestion problems. Typical problems include for example highly variable network response times, higher network failure rates, and the inability to support delay-sensitive applications.
Local area network (LAN) switches offer a quick, relatively inexpensive way to relieve congestion on shared-media LAN segments. Switching technology is emerging as a more effective means of managing traffic and allocating bandwidth within a LAN than shared-media hubs or simple bridges. LAN switches operate as datalink layer (Layer 2 of the OSI reference model) packet-forwarding hardware engines, dealing with media access control (MAC) addresses and performing simple table look-up functions. Switch-based networks are able to offer greater throughput, but they continue to suffer from problems such as broadcast flooding and poor security. Routers, which operate at the network-layer (Layer 3 of the OSI reference model), are still required to solve these types of problems. However, fast switching technology is overwhelming the capabilities of current routers, creating router bottlenecks. The traditional IP packet-forwarding device on which the Internet is based, the IP router, is showing signs of inadequacy. Routers are expensive, complex, and of limited throughput, as compared to emerging switching technology. To support the increased traffic demand of large enterprise-wide networks and the Internet, IP routers need to operate faster and cost less.
Additionally, quality of service (QOS) selection is needed in order to support the increasing demand for real-time and multimedia applications, including for example conferencing. Currently TCP/IP does not support QOS selection. However, as advanced functionalities required by more types of traffic are enabled in IP, traditional IP routers will not suffice as packet-forwarding devices.
Asynchronous transfer mode (ATM) is a high-speed, scaleable, multiservice technology touted as the cornerstone of tomorrow's router-less networks. ATM is a highly efficient packet-forwarding technology with very high throughput, scaleability, and support for multiple types of traffic including voice and video as well as data. However, ATM is a networking technology so different from current networking architectures such as IP that there is no clear migration path to it. ATM has difficulty in effectively supporting existing LAN traffic due to its connection-oriented architecture, which creates the need for an additional set of very complex, untested multi-layer protocols. Problems with these protocols are evidenced by unacceptably long switched virtual circuit (SVC) connection setup times. Additionally, enabling TCP/IP users to send and receive ATM traffic using SVCs requires adopting even more new, unproven, and extremely complex protocols. These protocols do not enable applications running on TCP/IP protocols to take advantage of the QOS features of ATM, thereby imposing a tremendous amount of overhead for network managers without enabling one of the key benefits of ATM. Also, many of these protocols duplicate the functionality of the well-established TCP/IP protocol suite, and the need to learn these complex protocols increases the costs of ownership of ATM devices for network managers who must troubleshoot problems in the network. The difficulties of moving to ATM are especially pronounced in light of the time-tested and debugged IP being solidly entrenched with its huge and growing installed user base as evidenced by the popularity of the Internet.
In response to the inadequacies of current solutions to the problems, vendors have developed a host of new distributed routing networking architectures. However, these architectures are often complex, confusing, and duplicative of functionalities provided by IP. These architectures also result in increasingly complex problems for network managers. For example, duplication of functionality leads to increased strain on the network management function and can make isolation of network problems very difficult. It is seen that a system for high speed routing is needed to avoid bottlenecks and increased network management complexity. Further, provision of a networking architecture having compatibility with IP without unnecessary duplication is needed.